This disclosure relates to an (oxy)nitride phosphor, a white light-emitting device including the (oxy)nitride phosphor, and a method of preparing a nitride phosphor.
Conventionally, fluorescent lamps and incandescent lamps are widely used as sources of luminescence. However, mercury (Hg) used in fluorescent lamps causes environmental problems and hence is not desirable. Moreover, these conventional sources of luminescence are not suitable for power saving due to their very short lifetimes and very low efficiencies. Thus, much recent research has been conducted to improve the efficiency of white light-emitting devices.
White light-emitting devices can produce white light by exciting three primary color (red, green, and blue) phosphors using a UV light-emitting diode (UV-LED) as a light source, by exciting red and green phosphors using a blue-LED as a light source, or by exciting a yellow phosphor using a blue-LED as a light source.
Among these three methods, the method of producing white light by exciting a yellow phosphor using a blue-LED as a light source leads to poor color reproduction due to the low intensity of red light.
Thus, research has been increasingly conducted to develop luminescence systems based on the other methods of producing white light by exciting phosphors using UV- and blue-LEDs. These methods can provide good color reproduction but display a low efficiency.
Meanwhile, commonly known red phosphors are not suitable for use in white light-emitting devices. These red phosphors exhibit good emission efficiency with respect to cathode rays, VUV (vacuum ultraviolet) rays, and short wavelength light, but poor emission efficiency with respect to UV and blue light when used in white light-emitting devices. Thus, in the technical field of white light-emitting devices, the development of red phosphors having high efficiency with respect to UV and blue light is strongly needed.
Under these circumstances, some nitride phosphors have been developed. The nitride phosphors emit light under UV and blue light, but the intensity of light is not sufficient to be commercially available for white light-emitting devices. Nitride phosphor preparation methods known hitherto use process conditions of high temperatures and high nitrogen gas pressures (0.1 MPa or more). Thus, a special apparatus designed to withstand high temperatures and high pressures is desirable. Moreover, unstable materials are used as starting materials, and thus, the stringency of conditions used to handle the starting materials increases. As such, red phosphors suitable for commercial production have not yet been developed.